Exhaust gas turbocharger with adjustable slide ring

Abstract

In an exhaust gas turbocharger with a radial or axial turbine and an at least partially radial flow turbine nozzle ring (8), a movable slide ring (2) makes possible an infinite adjustment of the turbine inlet cross-section. The movement of the slide ring (2), which slides between nozzle ring (8) and rotor blading (1), occurs by means of an axial displacement. The front edge around which the gas flows is shaped to conform with the flow in order to avoid downstream separations. With radial turbines, the inlet flow angle to the turbine rotor blading remains approximately constant over the whole control range. In consequence, the shock loss at the turbine rotor blading substantially disappears. The infinite adjustment of the turbine inlet cross-section results in an improved part load behavior of the supercharged engine because the air quantity supplied to the engine is matched to the combustion conditions and smokeless operation is obtained over the whole rotational speed range.

What is claimed is: 
     
       1. An exhaust gas turbocharger for an internal combustion engine, said exhaust gas turbocharger comprising: (a) a turbine having rotary blades, said rotary blades defining a cylindrical volume as they rotate;   (b) an at least partially radial-flow turbine nozzle ring comprising a plurality of circumferentially spaced guide vanes sized, shaped, and positioned to cause exhaust gas to flow therebetween in a direction, said plurality of circumferentially spaced guide vanes having downstream edges which lie on an imaginary cylinder which is spaced outwardly from the cylindrical volume defined by the rotary motion of said rotary blades; and   (c) a slide ring movable in the axial direction for altering the turbine inlet flow cross-section, said slide ring extending upstream between said nozzle ring and said rotary blades and being axially movable along the downstream edges of said guide vanes, said slide ring extending downstream beyond said rotary blades and having a radial internal contour which is closely spaced from the radially outer edges of said rotary blades over the entire axial travel of said slide ring and which forms the radial wall of a flow duct for exhaust gas downstream of said rotary blades.   
     
     
       2. An exhaust gas turbocharger as recited in claim 1 and further comprising means for biasing said slide ring against the force acting on the upstream end of said slide ring created by the difference in pressure of the exhaust before and after said rotary blades, whereby the axial positioning of said slide ring occurs automatically. 
     
     
       3. An exhaust gas turbocharger as recited in claim 1 and further comprising means for adjusting the axial position of said slide ring as a function of an engine parameter. 
     
     
       4. An exhaust gas turbocharger as recited in claim 1 wherein: (a) the surface of said slide ring adjacent to said nozzle ring is saw-toothed shaped;   (b) the spacing between the saw-teeth on said slide ring corresponds to the spacing between the spaced guide vanes in said nozzle ring; and   (c) the surfaces of said saw-teeth on said slide ring facing the gas flow are substantially perpendicular to the direction of flow of the exhaust gas.   
     
     
       5. An exhaust gas turbocharger as recited in claim 4 and: (a) further comprising a gas inlet casing;   (b) wherein said slide ring is axially movable along the radially inner surface of said gas inlet casing; and   (c) wherein said gas inlet casing is provided with saw-teeth corresponding to the saw-teeth on said slide ring.   
     
     
       6. An exhaust gas turbocharger as recited in claim 1 wherein the surface of said slide ring adjacent to said nozzle ring comprises a plurality of saw-teeth shaped so that they project in between the circumferentially spaced guide vanes in said nozzle ring and so that one surface of each of said saw-teeth is in sliding engagement with the leading surface of an associated one of said guide vanes. 
     
     
       7. An exhaust gas turbocharger as recited in claim 6 wherein the surfaces of said saw-teeth on said slide ring facing the gas flow are substantially perpendicular to the direction of flow of the exhaust gas. 
     
     
       8. An exhaust gas turbocharger for an internal combustion engine, said exhaust gas turbocharger comprising: (a) a turbine having rotary blades, said rotary blades defining a cylindrical volume as they rotate;   (b) at at least partially radial-flow turbine nozzle ring comprising a plurality of circumferentially spaced guide vanes sized, shaped, and positioned to cause exhaust gas to flow therebetween in a direction, said plurality of circumferentially spaced guide vanes having downstream edges which lie on an imaginary cylinder which is spaced outwardly from the cylindrical volume defined by the rotary motion of said rotary blades to define a gas flow passage therebetween;   (c) a slide ring which is axially movable along the downstream edges of said guide vanes into said gas flow passage and which takes up the whole radial width of said gas flow passage, said slide ring having a radial forward surface against which fluid in said gas flow passage acts to bias said slide ring out of said gas flow passage, said slide ring extending downstream beyond said rotary blades and having a radial internal contour which is closely spaced from the radially outer edges of said rotary blades over the entire axial travel of said slide ring and which forms the radial wall of a flow duct for exhaust gas downstream of said rotary blades; and   (d) spring means which bias said slide ring into said gas flow passage against the force applied to said slide ring by the fluid pressure in said gas flow passage,   whereby said slide ring automatically varies the effective cross-sectional area of said gas flow passage in response to changes in the fluid pressure in said gas flow passage.   
     
     
       9. An exhaust gas turbocharger for an internal combustion engine as recited in claim 8 wherein the upstream and downstream faces of said slide ring are rounded to conform to the flow of gases through said gas flow passage.